OF ARTS AND SCIENCES. 



63 



Professor Agassiz made a verbal communication on some 

 new species of cartilaginous fishes which he had discovered on 

 the coast of the United States, which were especially inter- 

 esting for the study of the relations existing between fossil 

 and living types. America contrasts strongly with Europe 

 in the number of living species belonging to genera of ani- 

 mals which also exist in a fossil state ; the old types are so 

 much more numerous here, that this continent to the paleon- 

 tologist has quite an old-fashioned appearance. 



The Port Jackson Shark is the only type of its family 

 now represented by a living species in the Old World. He 

 had found on our coast eight genera of cartilaginous fishes 

 not noticed before. The genus Carcharias is not found fossil, 

 and the living species are few. The genus Odontaspis, found 

 fossil as low as the chalk, has two representatives on our coast, 

 one in Long Island Sound, the other on the coast of South 

 Carolina ; to this genus he thinks the Squalus macrodon of 

 Mitchell belongs. To this genus, also, belong most of the fossil 

 teeth of our tertiary deposits ; many of these, previously con- 

 sidered as belonging to the genus Lamna, he was now, from 

 examination of living representatives, able to refer to their 

 true genus, Odontaspis. The old genus Lamna he had di- 

 vided into Lamna and his genus Oxyrhina. Of the genus 

 Galeocerdo, geologically very important, with teeth serrated 

 and curved backwards, he had obtained a species as far south 

 as South Carolina. Fossils of this genus are found in deposits 

 as early as the cretaceous ; the genus Galeus differs in the 

 serrations of its teeth. The large teeth found at Gay Head 

 and Marshfield belong to the genus Carcharodon. Dr. Andrew 

 Smith found a representative of this genus at the Cape of Good 

 Hope. Professor Agassiz had received a jaw of a living spe- 

 cies from Nantucket, and some teeth from Cape Cod, belonging 

 to this genus. This, then, is another of the old types found 

 on our coast. It differs generically from Carcharias ; the dif- 

 ferences do not depend so much on the position of the teeth 

 in the jaw, as on the structure of the teeth, which are hollow 



